Do you have OFB? If so, you could buy the lot and hire sims for the job. That probably isn't the way you're wanting to go, since it has limitations. Maybe someone who knows more about this can fill in. In any case, be careful with the npc creator gun. All the sims you choose not to keep are still given character files, and creating them in mass quantities will needlessly add to loading times. I learned that the hard way.